Control system



Nov. 5, 1935-. G. L. BEERS CONTROL SYSTEM Filed April 7, 1951' 2 Sheets-Sheet 1 IN V 1 fieoge fleets G. L. BEERS CONTROL SYSTEM Nov. 5, 1935.

Filed April 7, 1931 2 Sheets-Sheet 2 AP \m.

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UNITED STATES PATENT OFFICE amen oomoL srs-nm George Hale Beers, Collingswood, N. 1., aasignor, by mcsne assignments, to Radio Corporation of America, New York, N.

Delaware Y., a corporation of Application April 1, 1931, Serial No. me; 6 Claims. (01. 112-239) My invention relates to control systems and it has particular relation to systems whereby the tuning of a radio receiver may be accomplished from a remote point.

Remotely controlled continuous-tuning systems, as heretofore constructed for radio receivers, have not given entire satisfaction. A major defect of many of such systems is the difficulty of maintaining exact angular correspondence between the position of a local indicating device and the position of a distantly situated controlled element whereby the operation of tuning is, to

a certain extent, rendered a matter of guesswork.

Furthermore, substantially all remote control systems of the type generally characterized by the use of a reversible motor for driving the tuning element, have a tendency tooverrun" the desired adJustment. The over-running necessitates reversing the motor a number of times be- 'fore the proper position of the tuning element is obtained and, accordingly, causes a waste of energy and time on the part of the operator.

It is, accordingly, an object of my invention to provide a remote-control system especially adapted to radio receivers, though capable of general use, wherein exact angular correspondence is automatically maintained between the position of a local adjusting and indicating device and a distantly situated controlled element such as a tuning condenser, or the like.

Another object of my invention is to provide a remote-control system that is substantially independent of the rapidity with which the local indicating and adjusting device is moved from one position to another. i

Another object of my invention isto provides.

' system, of the type described, wherein the torque developed by the motive means is independent of the amount of adjustment of the controlled element or the extent of movement of thelocal ini dicating device.

Another. object of invention is to'provide aremote-control system, of the type described, wherein there is substantially no tendency for the distantlysituatedcontrolled element to "overrun the desired adjustment.

A still further and more specific object of my invention is to provide a remote-control system wherein means are provided for automatically. bringing the remotely situated controlled element 1 thereto I accomplish by providing, in one modifimentioned, to be equalized or reduced to zero 15 7 whereby the motor is deprived of armature current and comes to rest.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, 20 however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific em bodiment, when read in connection with the ac 25 companying drawings, in which:

I Fig. 1 is a diagrammatic view of a remote-control system including an embodiment of my invention, and

Fig. 2 is a diagrammatic view of a remote-con- 80 trol system comprising a preferred embodiment of my invention.

Refen-lng to Fig. 1, my improved remote-control system comprises a motor I, the shaft 3 of which is connected through a reducing gear 5 to 8 the shaft I of a tuning condenser 9. The field winding ll of the motor is supplied with 'alter-,

. is situated at a distance from the motor and the radio receiver. Q i In order that the motor may be driven in either direction, I provide two sources of armature current, the said sources preferably being constituted 45 by a pair of grid-controlled electric discharge rectifier or control devices l1 and I9. Electric discharge devices of the type known commercially as Thyratrons may be employed at H and I9. As' is well known to those skilled in the art, a device of the Thyratron type is an electrostatically controlled arcrectifier, the starting of the arc being controllable by the potential applied to the grid whereby the average rectified current output may be varied by varying the grid bias. Each ll of the said devices has a plate 2 a grid 28 and a cathode 25.

Cathode heating current is supplied from individual secondary windings 21 and 28 of a powertransformer 3|, a plurality of additional individual secondary windings 33 and 35 serving to impress alternating potentials between the plate and cathode of each of the rectifier or control devices I? and IS. The primary winding 35 01 the transformer 3| is connected to the same source that supplies field current to the motor.

The space current paths of the several electrostatically grid controlled arc rectifier tubes are differentially connected in shunt to the brushes of the motor preferably through individual transformers 38 and 40.

By reason of the difierential connection, current corresponding in phase and amplitude to the space current from the first arc rectifier traverses the armature of the motor in one direction, while current induced by the space current from the other are rectifier traverses the armature in the opposite direction.

The grid of the first rectifier device I1 and the cathode of the second rectifier device l9 are connected together and a conductor 31 extends from the junction point between them to the movable contact-arm 39 of a potentiometer 4| that is supplied with potential from any convenient D. C. source 43. A resistor 45 is preferably interposed between the movable arm of the potentiometer and the junction point referred to.

The terminals of the resistance element 41 of the potentiometer 4| are connected to the terminals of the resistance element 49 of an identical potentiometer 5| mounted upon or within the receptacle |5 which accommodates the switch Hi.

The contact arm 53 of the second mentioned potentiometer 5| is connected, through a resistor 55 and a conductor 51, to the cathode of the first mentioned device i1 and the grid of the second mentioned device IS.

The potentiometer 5| may be provided with a dial 59 calibrated in kilocycles or wave lengths whereon station indicia may be written.

The potentiometer 5| is hereinafter characterized as the local-potentiometer, and the potentiometer 4| will be referred to as the remotepotentiometer.

It will be noted, from an inspection of the drawings, that the grid potential of the device i1, with respect to its cathode, is the same as the potential of the cathode of the device IS, with respect to its grid, when the local and remote potentiometers are identically adjusted, and that, in such event, the said potentials are substantially zero. Grid biasing sources 42 may also be provided if desired.

Since, as is well-known to those skilled in the art, an electric discharge rectifier device of the Thyratron type becomes non-conductive when the grid is at zero potential or when it is sufilciently negative with respect to its cathode, neither of the rectifier devices in my improved system will conduct current when the potentiometer arms are each in the same relative position with respect to the termini of the two potentiometer-resistors.

If, for example, the positions of the various elements are as shown in the drawings, the grid and filament of the first rectifier or control device and the filament and grid of the second rectifier or control device are at the same potential since the drop in potential from the local potentiometer arm to the negative end of its associated resistor is exactly compensated by the rise in ptential from the negative end of the resistor 41 to the point at which the contact arm of the remote-potentiometer makes contact therewith. In this condition both of the rectifier devices are non-conductive and the motor is de-energized.

Assuming that it is desired to change the tuning of the system, the contact arm of the local-potentiometer is moved, as rapidly as desired, toward either the positive or the negative end of the resistor 49 associated therewith. An un- )0 balance is thus caused between the input potentials applied to the rectifier devices and, depending upon the direction of movement 01' the indicating device, one or the other of the said rectifier devices becomes conductive. If the contact arm is moved toward the negative end of the associated resistor, the device H, the grid of which is connected to the other potentiometer arm, becomes conductive, while if the contact arm is moved toward the positive end of its associated resistor, the other device I! conducts current.

Irrespective of which device becomes conductive, however, the application of currents from the transformer 38 or 40 to the armature of the motor, provided the secondary winding terminals of the transformers 38 and 40 are diiferentially connected to the brushes thereof, results in a slow change in the angular position of the tuning condenser 9 and an equal change in the position of the contact arm 39 of the remote-potentiometer, the movement continuing until the said arm reaches a point upon its resistor which is at the same potential as the point to which the local potentiometer arm has been moved on its resistor.

Should the motor over-run, the arm of the remote-potentiometer associated with the tuning condenser would be moved past the proper point, which movement would be equivalent to a movement of the local-potentiometer arm in the opposite direction and would result in automatic (0 reversal of the motor. If the reduction in speed between the motor and the tuning device is sufilciently great, however, or if braking means are provided, the tendency toward over-running" is substantially eliminated.

Inasmuch as a change of grid potential of 1/10 or 2/10 volts is sufilcient to control the rectifier devices, a tuning accuracy of one or two kilocycles may easily be obtained, provided the potential across the potentiometers is of the order of 100 volts and the potentiometer-resistors are of the proper size. If higher biasing potentials are used, greater accuracy may be obtained.

A volume-control-potentiometer 5| may be disposed within the receptacle I5, which houses the local-potentiometer and the switch ii, if desired, in which event an eight wire control-cable might be required. If the controlled receiver is supplied with automatic volume-control devices, however, by means of which the signal output level can be varied through the application of varying potentials to the grids of the amplifying tubes, a four or five wire cable would probably be sufilcient for all of the controls.

It also lies within the scope of my invention to utilize alternating potentials for the control of the rectifier devices. A modified system is diagrammatically shown in Fig. 2 oi the drawings wherein elements equivalent to those shown in 7 Fig. l are similarly designated.

The apparatus illustrated in Fig. 2 comprises the local-potentiometer 5| and the remote-potentiometer 4|, both potentiometers being supplied with A. C. potential from a secondary wind- 76 .The transformer 19 is also provided with a plurality of secondary windin'gsflt and Il i'orsupplying plate current to a plurality of grid-controlled electricdischarge rectifier or control'devices "and II o! the'Thyratron type, and for supplying cathodepotential to the said devices and a control-tube l9.

The control-tube may be of the screen-grid. equipotential cathode type having a plate 99, a

' control grid 91, a screen-grid 89, a cathode 9| and oi biasing'potential. I v I In the operation of the'remote-control system just described, the switch 13 is first closed, whereby the transformer 13 is energized and the radio" 7 a heater 9!. The plate and screen-grid may] be provided with appropriate potentials from any, I

convenient source, exemplified by a'battery-95 shown in the drawings, a resistor 99 being interposed in the plate-supply circuit.

An intermediate point 91 on the transformer n winding I6 supplying plate potentiaito the devices 19 and 9| is connected, through the primary winding 99 oi'a transformer IN and a limiting resistor I93, shunted by a by-pass condenser I95, to a conductor I91 common to thecathodesot the said devices.

Thesecondary winding I99 ot the last'mentioned transformer is connected in series with a' field winding ill oi'an induction-motor H2 01' the type known as a capacitor motor. The motor is provided. with an additional winding 9 which is connected, through a phase-shifting condenser I i5 across the conductors leading fromthe A. C. source previously mentioned. The armature of the motor is of the squirrel cage type and it may be connected through a suitable insulating coupling device to the tuning-reactor (not shown) and to the remote-potentiometer.

Inasmuch as the mechanical connections between the motor armature and the tuning condenser need be no different from those shown in Fig. '1',

they have not been illustrated.

' The grids of the rectifier devices are connected togetherrand the junction point I I9 between them is connected, to the cathodes through a grid resistor ill and a biasing battery 9 and to the plate 95 of the control-tube 93 through ablocking condenserlfl. i.

An individual resistor I29 is interposed between each 01 the control grids of the devices 19 and 8| and the junction point H6 for the purpose of limiting the grid currents drawn by said devices.

The control-grid 91 of the phase-control tube isconnected to the movable contact 39 of the remote-potentiometer 4i, while the cathode oi the said tube is connected 'to the contact arm' 53.01 the local-potentiometer 5|. through I a'source I25 receiver (not shown) is supplied with power. It,

' at the moment the switch is closed, the local and remote potentiometer arms are, respectively, in

contact with points upon theirassociated'resistors which are at the same potential, the input =potential'applied to the control-grid oi the phasecontrol tube is merely that furnished by the grid biasing source. In such event, the space' current' from the phase control tube, traversing'the output resistor 96 interposed between, the plate and the potentialsource 95, has no A. 0; component.

ducts current. and no current, according y, flows stantaneous plate and grid potentials thereof- That'is, if the grid of one or the other of said devicesis negative when a positive potential is im-- pressed upon the platecathode path therein from the secondary winding 15, no current will flow, while, on the other hand, iithe grid potential is positive at'the said instant, current will fiow, the 20 average amount oi currentflowing being a iuncin the primary winding 9| of thetranstonner I" the secondary winding of which supplies current to the field coil HI 0! the tuner-driving motor.-

Should it then be desired to alter the tuning of the phase of the current in the other winding, however, is dependent upon the relative conductivity oi the two are rectifier devices. The conductivity I or the devices, in turn,is dependent upon the intion oi. the phase angle between the grid and plate potentials.

' It, therefore, the local-potentiometer isfmoved' toward one end or the other of itsassociated resistor, an alternating potential is added to the I potential supplied by the local biasing source 5,,

the phase of the said added potential with respect to the phase of the potentials impressed upon the I plates of the devices 19 and BI being determined 90 by the direction in which the local-potentiometer contact arm is moved with respect to the position of the remote-potentiometer contact arm. Alternating potentials are, accordingly, developed across the output resistor 96 in the plate circuit of the control-tube and are impressed upon the grids'of the devices 19 and 8! either in or out of phase with the potentials being impressed across the plate cathode paths therein. Depending upon the phase of the impulses iin pressed on said rectifier devices from the control tube, one or the other of said devices becomes conductive and the output current therefrom,

, with respect to the phase of the currents in the other coil being advanced, or retarded, depending upon which or said devices is conductive.

Any movement, therefore, of the local potentiometer arm to one side or the other of the position corresponding to the position of the rei mote-potentiometer contact arm results in a reversal of the. phase of the current applied to the coil II I a of the tuner driving motor resulting in "rotation oithe armature of the said motor in one direction or the other. I

Inasmuch as the remote-potentiometer contact arm is driven by the motor, it is caused to move f over its associated resistor until zero alternating potential exists between it and-the local potentiometer contact arm. As soon as zeropotentialexists, indicating correct adjustment of the tuning reactor, the rectifier devices are deprived oi A. Q'input excitation. from the phase-control tube andbecome non-conductive. Non-conductivity ofthe rectifier devices results in'deprivlng the tuner driving motor of thatpart. of its field current which is contributed by the transformer 701i Ill and the motor, since the torque supplied by the coil I I3 alone is not sufficient to overcome the resistance of asmall brake (not shown), comes to rest without hunting. a I U "It ,will be apparent, from a consideration oilthe foregoing description oi my improved remotecontrol system, that I have eliminated all guesswork from the remote-control of the tuning of a radio receiver since the position of the local indicating device and the position of the tuning reactor are positively constrained to correspond.

My control system is also advantageous in that substantially the full torque of the driving motor is developed upon the slightest movement of the local-potentiometer, thus enabling the actuation of relatively large tuning elements having appreciable inertia.

It should further be apparent that my improved system, being semi-automatic in operation, obviates all necessity for manually reversing the tuning-reactor driving-motor a plurality of times in order that a desired adjustment may be obtained.

Although I have illustrated and described several specific embodiments of my invention, many modifications and many other fields of application thereof will be apparent to those skilled in the art to which it pertains. My invention, therefore, is not to be limited except insofar as is necessitated by the prior art or by the spirit of the appended claims.

I claim as my invention:

1. The combination with an alternating current electric motor having a pair of balanced op rating circuits, of a pair of grid-controlled electric discharge rectifier devices connected each in one of said circuits, circuit means for supplying alternating current to said rectifier devices in opposite phase relation and to said circuits separately each through one of said devices, a common direct current source of biasing potentials for said devices connected between the input electrodes thereof, adjustable means in circuit between said source and one of said devices for varying the biasing potentials applied to said devices from said source, and adjustable means connected between said source and the other of said devices for compensating for variations caused by adjustment of said first named means, said last named adjustable means being connected with the motor, whereby it is adjustable in response to operation of the motor.

2. In an alternating current motor control network, the combination of a pair of grid-controlled electric discharge devices, a pair of motor supply circuits, means for supplying alternating current to said circuits through said devices in opposite phase relation, and a grid, control circuit for said devices including a common source of biasing potential, a pair of potentiometers connected in parallel thereto and each having a variable tap point, circuit means providing a connection between each of said tap connections and the grids of said devices, means for moving one of said tap connections to simultaneously apply differing potentials to said devices, and means connected with the other of said tap connections to move it to equalize said difiering potentials.

3. The combination with an alternating current electric motor, of means for controlling the operation thereof, including an alternating current supply circuit to which said motor is connected to receive operating current therefrom, a pair of grid-controlled electric discharge rectifier devices of the Thyratron type connected in opposite phase relation to each other and in parallel with respect to the motor between said alternating current supply circuit and said motor for supplying further operating current thereto, a pair of controlling potentiometers, a source of controlling potential for said devices with which 5 said potentiometers are connected in parallel, said potentiometers each having a variable tap connection, means connected between said variable tap connections for applying a variable control potential to said rectifier devices, and means 10 for independently varying said tap connections, said means including an operating connection between the motor and one of said tap connections.

4. A control system for an electric motor including in combination, an alternating current 15 supply circuit for said motor, a second supply circuit for said motor, a pair of grid-controlled electric discharge devices of the Thyratron type connected between said first and second named supply circuits, means including a common direct 2. current source of biasing potential and a control circuit for controlling said devices, and a pair of controlling potentiometer devices connected in parallel between the control circuit for said devices and said source, for controlling the flow of 23 current from said first named supply circuit to said second motor supply circuit.

5. In a remote control system for radio apparatus, a pair of potentiometer devices, an alternating current supply circuit connected in par- 30 allel with said devices, an electronic control device having a cathode connected with one 0! said potentiometer devices and a control grid connected with the other of said potentiometer devices to receive a control potential therefrom, a 33 pair of grid controlled electric discharge rectifier devices, an output circuit for said control device connected with said rectifier devices to supply grid potentials thereto in parallel, said rectifier devices having output circuits connected in op- 40 posite phase relation to said alternating current supply circuit and having a common output circuit to which said rectifier devices are connected in parallel relation, and an alternating current motor having a winding connected with said alll ternating current circuit and a second winding connected with said last named rectifier output circuit.

6. Apparatus for positioning an object with respect to the position of a controlling device, I. comprising a motor, energizing windings for running said motor in one direction or the other according to the phase relations between electromotive forces impressed upon said windings, means including separate electronic devices, each II for deriving opposite half-wave rectification of an alternating current source for directly energizing one of said motor windings, means permanently coupling the other of said motor windings directly to said source, and phase-shifting bal- M ancing means operable in part conjointly with said object to be positioned, and in part conjointly with said controlling device, for selectively controlling said electronic devices one at a time, to feed constant current therethrough for 6 running said motor in the desired direction up until said object is moved by said motor into the desired position, whereby a balance is restored to said balancing means.

70 GEORGE LISLE BEERS. 

